1. Field of the Invention
The present invention relates to a method and system for correcting an image distortion occurring when an original image as captured or created is projected on a screen.
2. Description of the Related Art
Due to a difference between a projecting method used to capture or create an original image and a projecting method used to project the original image in a planetarium, or when the image is projected onto a spherical screen, the image suffers from distortion. To reduce or eliminate this distortion of the projected image, JP-2002-14611 discloses a video projecting method which converts each pixel position on an original image to a position at which a projected image is less distorted or free from distortion to sequentially generate post-conversion pixel position data, sequentially generates projection image data for each frame after the pixel position conversion from input projection image data and post-conversion image position data, and emits a projected image from an output device, thereby correcting each pixel position on the original image when it was created to project the correct image.
A means proposed for correcting such distortion of a projected image may project an auxiliary line from a projector onto a curved screen as a test pattern, and manipulate the auxiliary line displayed on a user interface display area on a display of a personal computer, while viewing the image of the projected auxiliary line.
FIGS. 1 and 2 illustrate an example of correcting distortion of a projected image when it is projected onto cylindrically curved screen 11 by projector 12, wherein predetermined auxiliary line 14 is drawn on user interface screen 13a on a display of computer 18, and auxiliary line 14 is transformed on a display area defined for user interface screen 13a, on which auxiliary line 14 is displayed, to correct distortion of the projected image. Line 16 illustrates the connection between the computer 18 and the projector 12. FIG. 1 illustrates the image before the correction for distortion, while FIG. 2 illustrates the image after the correction for distortion.
First, as illustrated in FIG. 1, a rectangle, for example, is displayed with straight auxiliary line 14 on the display area defined for user interface screen 13a. Auxiliary line 14 is projected onto cylindrically curved screen 11 from projector 12 through video cable 17. The auxiliary line projected onto curved screen 11 appears to be a distorted image due to the curved shape of screen 11, rather than a rectangle composed of straight line segments, so that auxiliary line 14 displayed on the display area for user interface screen 13a is transformed or modified as illustrated in FIG. 2. Transformed auxiliary line 14 thus transformed is projected onto cylindrically curved screen 11 from projector 12 through video cable 17 to adjust the transformation of auxiliary line 14 on user interface screen 13a on display 13 such that the projected image of the auxiliary line approaches to a rectangle composed of straight line segments.
Then, when auxiliary line 14 projected onto curved screen 11 fits to a rectangle composed of straight line segments, variables corresponding to transformed auxiliary line 14 at this time are saved as correction data. By correcting image data projected from projector 12 using the correction data, a projected image can be geometrically corrected to display the projected image which has been corrected for distortion on curved screen 11.
The foregoing distortion correcting technique using auxiliary line 14 can experience auxiliary line 14 extending out of the display area for user interface screen 13a as illustrated in FIG. 3 when a correction should be made beyond the display area for user interface screen 13a, or when the display of computer 18 has a resolution lower than that of projector 12. In this event, a problem arises in that the behavior of auxiliary line 14 cannot be confirmed out of the screen.
Since a general-purpose personal computer is often used as computer 18, the resolution of projector 12 is not always the same as the resolution of the display associated with such a personal computer on which the user interface screen is displayed. For this reason, when projector 12 has a higher resolution than that of the display of the personal computer, auxiliary line 14 must be corrected over an area beyond the display of the personal computer, causing auxiliary line 14 to extend out of the display area for user interface screen 13a. This would result in a failure in drawing auxiliary line 14 within the display area for user interface screen 13a, thereby making the correction for distortion more difficult.